Metal hydride powder composites (MHPC) were manufactured employing the copper-encapsulation technique. Thermal conductivity and permeability of the unactivated MHPC were measured at k(eff) similar to 5 W/mK and K-H2 similar to 5 x 10(-15) m(2). Preliminary measurements of permeability of an activated MHPC appear to show permeability is increased; hysteretic behavior was observed. Since there are several transport phenomena occurring when reaction is going on, it is not easy to separate them. Nevertheless, the measurements obtained from the activated MHPC clearly behaved in a different fashion than the unactivated MHPC. The MHPC were used in two prototype fast reactors. Falling pressure characterization of their performance confirms that the obtained values of k(eff) and K-H2 are useful in applications such as heat pumps.